You Are Here: Management Updates 2001 Archive August 30, 2001

Date: August 30, 2001
Category: Insects
Subject: White Grubs, Caterpillars, Drought

WHITE GRUBS
We are getting increasing reports of grub activity throughout the state - on golf courses, home lawns, athletic fields, cemeteries. In some areas grub activity has coincided with drought stress, and skunks or raccoons are beginning to ravage those sites. In other areas (notably sections of eastern Massachusetts), occasional rain has kept grass growing well and has masked grub activity.

Turf managers who are responsible for areas that have had a history of grub activity probably should monitor those sites during the next week or ten days. If grubs are present above threshold levels (ranging from 6 to 15 grubs per square foot, depending on the species), you may want to consider taking action. Unfortunately, we are far enough into the life cycle that options are very limited now. The only products that will have an impact on grubs at this point are relatively fast acting materials ... trichlorfon (Proxol or Dylox), bendiocarb (Turcam), or isofenphos (Oftanol) are among those that could be considered.

IT IS TOO LATE to use imidacloprid (sold under the trade name Merit for commercial applicators) this year. If a turf manager wishes to use halofenozide (sold as Mach 2 and other trade names), the application should be made VERY soon. Halofenozide apparently has limited curative action, so you can get some relief as long as applications are made before grubs molt to the third and final stage. NOTE - halofenozide tends to be much less effective against oriental beetles and European chafers than it is against Japanese beetles, so late season applications (i.e., ones made between now and 5 September) probably should be limited to Japanese beetle populations only. Also be advised that we are already seeing large second instars and small third instars in many locations around the state, so in my opinion, it is already too late to use halofenozide in many areas.

STRANGE CATERPILLARS
Two different golf course superintendents sent us specimens of caterpillars that were apparently showing up in large numbers on putting greens. Because of the recent "scare" surrounding armyworms, they wanted to be certain these caterpillars were not a new infestation of those dreaded marchers. It turns out that the caterpillars were in fact "introduced pine sawflies" (Diprion similis), a species of hymenopteran insect. Sawflies have six or seven pairs of "prolegs" (fleshy protrusions) on the abdomen, while most turf-attacking caterpillars have four or five pairs of prolegs. The introduced pine sawfly is black with yellow and white blotches long the side of the body.

We know very little about the life cycle of the insect, but it usually completes two generations a year in the Northeast. It feeds on a wide range of pine species. I presume the caterpillars leave pine trees just before they pupate in late summer. The sawflies are not damaging to turf but can appear in numbers that are sufficient to present a major nuisance. Hang in there - they are just "passing through".

DROUGHT-STRICKEN LAWNS
Just a reminder - many lawns in the western part of the state are parched and well beyond dormancy. Some of those lawns have succumbed to chinch bug attack, and may not recover in September (assuming we ever get some rain!). If renovation is planned, consider using turfgrass cultivars that contain endophytes. These endophytic cultivars will provide protection against chinch bugs and billbugs in future years, and often are more drought-tolerant than non-endophytic cultivars.

- Submitted by: Dr. Pat Vittum